Odd Exhaust Valve Image

[smwash02]

PHOTOS

I'm working on my annual and I usually grab compression a few days before we really start so I can brace myself/order the needful. This year we landed on 78 78 62 79. Unsure of if it was a seating or beginning of a burned valve, I scoped it to see what was up. I see of a bit of a burn starting on one edge, is what it is. But what caught our eyes is what was going on in the middle of the valve.

Here is an album of the intake and exhaust valves for every cylinder (I think it shows 3 1 4 2, but mind the descriptions). #3 is my 62/80. Note the odd ring in the center. They all seem to have this look, but not as pronounced. I've gone over the valve safety poster and none of their examples have this on them. My A&P/IA said he's never seen something like that before.

Anyone else seen this? I'm going to go through the logs shortly and get the times on the rest. Gonna be a real bummer if I'm going to have to pull these guys.

1: 1/8/16 111 hours

2: 2/5/15 206 hours

3: Unknown, I need to dig deeper in my logs, but possibly during overhaul (3/20/93, 995)

4: 6/12/12 387

Edited September 24, 2017 by smwash02

[Browncbr1]

The chunks on the valve look like lead deposits to me.   Do you do a lot of short, lower power local flying?   You might try running Alcor TCP with your fuel and running harder/hotter...    

you may be able to just lap that valve seat, but would go ahead and ream the guide while you're in there, since the valve seems to be coked.  

[smwash02]

Thanks for the reply. My median/average flight over the past 5 years is around an hour. Year to date average is around 1.7 hours. I generally choose 6-8 for shorter flights and 9-12 for longer. I lean aggressively on the ground, in small increments in the climb as I feel it being too rich (holding an airspeed to keep temperatures under 400), and lean to stumble and back in a few clicks in cruise. I only have a CHT probe on one cylinder.

I've attached the primary area of concern, that bluish circle. Are you saying you think those are deposits? The intake chunks look very much like lead deposits.

[ArtVandelay]

I run LOP, and have the inner circle as well, my theory is the hollow stem valves (filled with sodium to enhance heat transfer), cause that area to run a little cooler, a little more lead deposits:

 

[N201MKTurbo]

I have to agree the little circle is just melted lead deposits. I find it in spark plugs all the time.

But the burn mark in the edge of the valve is a problem. That cylinder needs help. No need to pull them all off, just fix the bad one.

[Browncbr1]

Yea, I think so.  Hopefully just lapping the seat and honing the guide will kee that valve serviceable.  If it were me, I would go ahead and do it before flying again, the scope it again after 25 hours when changing oil.  

[mike20papa]

I read your initial post and have just been through a similar experience with my A model.  About 350 hrs on 4 new ECI cylinders, field OH engine.  I operate my engine in a very similar fashion to your description, so I feel I should probably pass this recent experience on.   I have had #2 & #4 cyl.s show the low 70's at annual.  #1 & #3 show high 70's.  The numbers are okay by the book, I know.  But pulling the prop thru (backwards) you could really feel the low compression and oil consumption was not favorable.  A bore scope showed scoring to the nickle carbide cyl.s (the valves looked similar to your photos) so I thought I'd pull the cyl's and send them off for OH.  I use J&J Airparts in Pleasanton, TX.  Long story short, found out my exhaust valves were beyond service limits and valve guides also.  So, you can email them for a quote or questions concerning cyl. repairs.  You could attach the photo album and get an opinion from the experts.  Just as a note .. they looked at my exhaust valves and asked " what are doing with that airplane, ..anyway?"  Needless to say I'm no longer leaning my engine like I have heard so many say does it no harm. 

[carusoam]

Valve thoughts....

Private pilot's look for concentric circles and edge effects...

The exhaust valves are hotter than the intake valves and have the tendency to have issues more than intake valves...

The edge effect looks kinda like the moon obscuring the sun...

#3 exhaust is showing an edge effect, but not as strong as some we have seen on MS...

#2 exhaust is showing an off center effect where the deposits are being affected unevenly, not concentric...

Private pilot ideas only, not a mechanic...

Best regards,

-a-

 

[smwash02]

Thanks for the advice all.

I'll be lapping the valve and reinspecting at oil change and seeing where we are in appearance and compression. I've done this procedure before and got another 50-60 hours out of that one before it started to slide.

@mike20papa There are likely some with good experience with ECI cylinders, but I'm not one of them. A guy on my other forum is a pipeline pilot and said they go through ECIs more quickly than others. Are you suggesting the cruise leaning is too hard? Without 4 CHT and EGT it's possible, but if I feel if I were overly lean we'd not see the center deposits. J&J is a short trip from me and I've used them in the past. Thanks for your personal experiences here. Seems like something was very wrong to have all 4 with bad valves so soon and scoring to boot.

Having only had the plane for ~350 hours, it's hard to know what all those cylinders (#3, #4) experienced. I've done many repairs for defects that would've had a negative impact on cylinder health (intake leaks, exhaust leaks, carb, mags, plugs, dog house, baffles, engine mounts) in the 4 years I've owned it.

As for #2, I'm not sure if it's off center or early edge effect. It will need observation too, it seems as if oil is leaking by; however, my consumption is decent. A quart every 12-14 hours. Exhaust looks good.

Edited September 25, 2017 by smwash02

[DXB]

The valve center deposits are likely irrelevant. Unfortunately your #1 exhaust looks like a  problem - the asymmetry in coloration is clear  (note I increased contrast in the image to make the crescents at the edges more visible). Maybe someone did a sloppy job with reconditioning that one at 111 hours ago?  The borderline compression on #3 is a separate issue, but if it is real and you are going to pull #1, it would be a good time to pull and IRAN #3 as well since it is  on the same side.  

[smwash02]

1 hour ago, DXB said:

The valve center deposits are likely irrelevant. Unfortunately your #1 exhaust looks like a  problem - the asymmetry in coloration is clear  (note I increased contrast in the image to make the crescents at the edges more visible). Maybe someone did a sloppy job with reconditioning that one at 111 hours ago?  The borderline compression on #3 is a separate issue, but if it is real and you are going to pull #1, it would be a good time to pull and IRAN #3 as well since it is  on the same side.  

Thanks for this. The image you've included is #3, which is the one I can't seem to find if it's been replaced since overhaul. It will have at least 400 hours on it. I intend to lap it and observe at next oil change to see if it can be saved.

Edited September 25, 2017 by smwash02

[Andy95W]

Nice catch, Dev.

[N201MKTurbo]

FWIW

My bosses B36TC had a valve that looked like your #3. We borescoped it about every 10 hours for about 25 hours. It only got worse. His engine was past TBO so I told him he better plan on flying it to Oaklahoma for overhaul while it is still running.

The overhauler said that burned valves are almost always caused by loose or warn valve guides or valve stems. This lets the valve seat uncentered. 

It really doesn't matter, when they overhaul a cylinder they have to measure all that, so they have to replace whatever is out of spec.

[smwash02]

13 minutes ago, N201MKTurbo said:

FWIW

My bosses B36TC had a valve that looked like your #3. We borescoped it about every 10 hours for about 25 hours. It only got worse. His engine was past TBO so I told him he better plan on flying it to Oaklahoma for overhaul while it is still running.

The overhauler said that burned valves are almost always caused by loose or warn valve guides or valve stems. This lets the valve seat uncentered. 

It really doesn't matter, when they overhaul a cylinder they have to measure all that, so they have to replace whatever is out of spec.

Thank you for the data point and I suspect this is what's going to happen, but takes me about 2 hours to lap a valve and do a wiggle test compared to 4-5 times that to do a cylinder replacement because of the dog house, so I figure it's a minor investment if it might pan out.